Various arrangements have been contrived to provide an upper seal for vessels containing food substances to inhibit the circulation of air at their upper surface as the items or substances are removed from the container. One example of such a seal is shown in U.S. Pat. No. 551,540 issued on Dec. 17, 1895 for "Liquid Dispensing Apparatus." That patent shows a float containing and emitting a sealing liquid used to shut off the air from liquid in a vessel. The sealing liquid at elevated temperatures, such as would be experienced with heated and reheated liquids, would be inoperable and indeed would contaminate the liquid itself. The liquid container float shown in that patent provides a substantially different and inferior sealing system from that of the present invention.
Other arrangements have been known to the prior art in which there is a preserving container in which fruit or solid other food particles are submerged within a vessel and in which the food particles are futher contained in a liquid to further the preservation of the food particles. This problem encountered and solved with respect to the prior art of this type is that there is used a follower cover to preserve food products through a pressure plate. The follower cover, when weighted down, keeps the food particles under the upper surface level of the liquid. The problem encountered and solved by prior art devices similar to this is not that of "keeping air from a liquid food substance" but rather of "keeping the solid food substance particles under the upper level of a liquid" and, in line with this approach, the floating lid ordinarily does have an escapement opening which permits liquid to pass through the lid and to remain in all cases in contact with the ambient atmosphere contained between the outer and the inner lids used in the combination. This type of prior art device is shown and described in U.S. Pat. No. 1,948,353 issued on Feb. 20, 1934 to J. L. Lagorio for "Preserving Container."
None of the prior art devices or systems is effective after the manner of the present invention to provide a properly controlled movement of a lid device so that the upper level of the liquid food is continuously followed during heating and reheating and during subsequent depletion from the container in such manner as to completely eliminate its contamination by contact with the air enclosed in the container or with ambient air so that bacterial contamination and loss of flavor of the liquid substance is completely inhibited. It will be understood that any liquid food substance is subject to contamination because of the bacterial or chemical reactions contained in the air regardless of the temperature at which the air or the liquid is maintained.
The present invention is directed toward the specific embodiment of a container for coffee in which, for example, the coffee is initially cooked and from which it is later served in successive individual portions over a period of hours or even days. It will be further understood that the present invention is equally applicable to thermos-type containers in which coffee has already been precooked in another container and is then stored in such manner as to retain its heated condition.